What do you need to know about WDR?
2023-02-01
What to do if you need to install monitoring at the entrance to the building, e.g. in a hall with many windows? In such circumstances, the capture of a clear and detailed image is hindered by the harsh light entering from the outside. The solution to this problem is the use of a surveillance camera with good WDR (Wide Dynamic Range) technology.
What is dynamic range?
Dynamic Range refers to the ratio between the largest and smallest measured value. In video recording, dynamic range determines the ratio between the lightest and darkest parts of an image.
WDR technology is perfect for high-contrast scenes, balancing the image so that it does not appear too bright or too dark.
Dynamic range is measured in decibels (dB). IHS specifies a WDR of 60 dB or higher, many camera models now have a WDR of 120 dB. Note that each manufacturer has their own method of determining the dB range.
How does WDR work?
WDR technology in surveillance cameras (e.g. model Dahua HDCVI 6.0 PLUS) may have a digital version – DWDR or True WDR.
True WDR uses image sensors and a Digital Signal Processor to ensure uniform illumination of all areas in the frame. The camera with True WDR has sensors that scan each image frame twice. The first time at low speed (to capture more light) reflects the view under normal lighting conditions. The second scan is performed at high speed to capture less light and produce an image with strong background light. The DSP processor combines both scans to create one image that is balanced and has an even level of illumination.
DWDR while uses algorithms instead of sensors to digitally level the image. It relies on a DSP chip instead of an image sensor. The algorithm adjusts every single pixel of the image and calculates its exposure. However, this technique has some limitations. A lot of interference and changes result in a grainier image. On the other hand, DWDR is a more economical option because it does not require the use of expensive image sensors.
Image exposure without WDR
There are two ways to improve image exposure without using Wide Dynamic Range technology.
In the case of a high-contrast scene with a strong background light, the camera will record an image with an average level of lighting, which will result in a darkened image.
If WDR is not available, BLC (Blacklight Compensation) can be used. This technology brightens the image to make darker details more visible. BLC is an older solution used by DSP processors to increase the exposure level for the entire image. WDR is a more advanced solution because it does not brighten the entire scene, but tries to balance the brightness levels for specific areas of the image.
l
HLC (Highlight Compensation) is a technology based on detecting by image sensors highly exposed places and reducing the exposure in these areas. This improves the overall image quality. In the case of a generally poorly lit scene with brightly lit spots (e.g. spotlights, lamps, etc.), the final image may be too dark. If the WDR function is not available, the HLC will compensate the brightness and align the image. The camera automatically suppresses bright light sources, allowing the correct exposure of adjacent areas.
Regardless of the dB value set in the camera, the image we get will differ depending on the specificity of the scene and the amount of movement in it. To choose the surveillance camera that will work best in a particular place, it is best to consult professionals.
Feel free to contact our customer service!